I am currently in the process of planning our new shop layout and have been giving some thought to an air line system to run through the shop for air tools. I have a friend who ran hard copper lines in his shop for air and it’s been fine for the last 6 or 7 years. Anyone know of any problems with this, and what pressure copper with soldered fittings is approved for? I know they use soft copper on our gas powered and electric portable compressors, but connections seem to be compression fittings on those. I would rather work with copper than black iron as I have the tools on hand, but if there is a big problem with copper I could stick with iron.